The Gene Silencing Section, (GSS) Genetics Branch, aims to be a group with specific expertise within CCR for the study and application of RNAi in mammalian cells. The scientific and clinical developments in the field of RNAi are rapidly impacting our understanding of the role of RNA silencing mechanisms on the control of normal and disease related gene expression, including cancer. Further, technological developments utilizing the RNAi mechanism have been developed for the analysis of gene function and the development of new model systems. More recently RNAi based analysis has been used for improved understanding of drug: target interactions and target identification, and these strategies are now being scaled to enable large scale screening, potentially up to whole genome. In addition to our project based research (see other project reports) we have played an extensive role in assisting and training CCR investigators in the use of RNAi for gene function analysis including, though not limited to, the training of Investigators and Post Doctoral Fellows in different aspects of RNAi analysis technologies, the sharing of protocols and RNAi characterization data (see below), as well as direct collaboration. To develop our first large scale RNAi effector resource Dr. Caplen, the GSS section head, developed a research collaboration agreement (RCA #2-18668-05, AKA MTA 18668) between the Gene Silencing Section, OSTP, OD, CCR (as of June 2006 GSS became aligned with the Genetics Branch, CCR) and Qiagen Inc. We have enabled CCR investigators to access confidential RNAi analysis data for 100 human genes, and this has resulted in the execution of over 30 intramural Material Transfer Agreements and the transfer of appropriate information to CCR investigators. As a direct result of data gathered as part of the initiative, plus additional collaborative work by Dr. John Weinstein's group, LMP, CCR) a patent application has been filed (full details are described in project Z01 BC 010613). Further, work with LBC, CCR (Drs. Gottesman, Ludwig and Szakacs) (detailed in project Z01 BC 010609) has enabled validation of a relationship between the expression of MDR1 (ABCB1) and a novel drug (NSC77360). This work has contributed to this small compound being further studied as part of a joint CCR/NCI-DTP drug development initiative. Dr. Caplen, the GSS section head has also been involved with two additional collaborative projects published in 2006. One study investigated the alternative delivery methods of synthetic siRNA and the other examined in vivo application of synthetic siRNAs to the respiratory system. These studies illustrate the sections commitment to stay aware of different strategies for delivery of RNAi effectors and we have assisted a number of CCR investigators considering or actually conducting, in vivo RNAi analysis. We have also been actively pursuing the development of even larger scale RNAi resources that can be used for high-throughput RNAi screening. Our resources by end FY06 will include, the library of 900 siRNAs (450 human genes) developed under a RCA with Qiagen Inc. and detailed above, a commercial siRNA library sufficient for 900 data points/siRNA and corresponding to 7,000 human genes representing the "druggable genome" and a replicated retroviral based shRNA whole human genome RNAi library. The aim of obtaining these resources and the expertise to use them has been to develop a collaborative program that CCR investigators can access for larger scale RNAi analysis than they would be able to perform within their own laboratories. Further, the recent placement of GSS within the Genetics Branch, CCR now gives us a unique opportunity to combine the RNAi expertise of GSS with the genome-wide analysis expertise of Dr. Meltzer's group and other groups within the Genetics Branch.